Merge branch 'jr-web-ide-core-docs' into 'master'

Web IDE is now GA

Closes #45307

See merge request gitlab-org/gitlab-ce!18403

doc/user/project/index.md

@@ -45,6 +45,7 @@ and time spent on
 templates for issue and merge request description fields for your project
 - [Slash commands (quick actions)](quick_actions.md): Textual shortcuts for
 common actions on issues or merge requests
+- [Web IDE](web_ide/index.md)
 
 **GitLab CI/CD:**
 

doc/user/project/web_ide/index.md

@@ -0,0 +1,34 @@
+# Web IDE
+
+> Introduced in [GitLab Ultimate][ee] 10.4.
+> Brought to [GitLab CE][ce] in 10.7.
+
+The Web IDE makes it faster and easier to contribute changes to your projects
+by providing an advanced editor with commit staging.
+
+## Open the Web IDE
+
+The Web IDE can be opened when viewing a file, from the repository file list,
+and from merge requests.
+
+![Open Web IDE](img/open_web_ide.png)
+
+## Commit changes
+
+Changed files are shown on the right in the commit panel. All changes are
+automatically staged. To commit your changes, add a commit message and click
+the 'Commit Button'.
+
+![Commit changes](img/commit_changes.png)
+
+## Comparing changes
+
+Before you commit your changes, you can compare them with the previous commit
+by switching to the review mode or selecting the file from the staged files
+list.
+
+An additional review mode is available when you open a merge request, which
+shows you a preview of the merge request diff if you commit your changes.
+
+[ee]: https://about.gitlab.com/products/
+[ce]: https://about.gitlab.com/products/